CD39-IN-1 (Compound 338) is a selective small-molecule CD39 inhibitor with an IC50 value of 68.7 nM. CD39-IN-1 shows anti-proliferative activity on tumor cells. CD39-IN-1 blocks CD39-mediated eATP hydrolysis in the ATP-adenosine pathway. CD39-IN-1 is promising for research of cancers[1].